DSA-4010-1 git-annex -- security update

It was discovered that git-annex, a tool to manage files with git
without checking their contents in, did not correctly handle
maliciously constructed ssh:// URLs. This allowed an attacker to run
an arbitrary shell command.

For the oldstable distribution (jessie), this problem has been fixed
in version 5.20141125+deb8u1.

For the stable distribution (stretch), this problem has been fixed in
version 6.20170101-1+deb9u1.